Last Modified: Aug 19, 2026
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
11.5.1, 11.5.1 hf1, 11.5.1 hf2, 11.5.1 hf3, 11.5.1 hf4, 11.5.1 hf5, 11.5.1 hf6, 11.5.1 hf7, 11.5.1 hf8, 11.5.1 hf9, 11.5.1 hf10, 11.5.1 hf11, 11.6.0, 11.6.0 hf1, 11.6.0 hf2, 11.6.0 hf3, 11.6.0 hf4, 11.6.0 hf5, 11.6.0 hf6, 11.6.0 hf7, 11.6.0 hf8, 11.6.1, 11.6.1 hf1, 11.6.1 hf2, 11.6.2, 11.6.2 hf1, 11.6.3, 11.6.3.1, 11.6.3.2, 11.6.3.3, 11.6.3.4, 11.6.4, 11.6.5, 11.6.5.1, 11.6.5.2, 11.6.5.3
Fixed In:
12.0.0, 11.5.2
Opened: Jul 24, 2014 Severity: 3-Major Related Article:
K16312
After STARTTLS handshake, SMTP communication fails due to one of the following reasons: - BIG-IP system responses to SMTP client are not synchronized (that is, the responses do not match the requested commands). - SMTPS profile activation mode is 'require' and the BIG-IP system responds with '530 Must issue a STARTTLS command first.
SMTP communication using the SMTPS profile might not succeed. intermittently or consistently.
This occurs when the following conditions are met: -- A virtual server configured with an SMTPS profile. -- After the STARTTLS handshake on the client side and the BIG-IP system has sent an RSET command to SMTP server, the BIG-IP system receives a command (such as HELO or EHLO) from an SMTP client before the BIG-IP system receives the RSET response from SMTP server.
None
SMTP commands received after STARTTLS are now correctly buffered by SMTPS profile until the SMTP server is ready to receive them.